Quantitative study of the production and properties of alginate/poly-L-lysine microcapsules

Alginate-polylysine-alginate (APA) microcapsules are of particular interest for their application as implants or for bioreactor cultures. Although their formation has been widely studied, there is still a lack of quant. data describing resistance, membrance thickness and permeability. In this study, the quant. application of a Texture Analyzer for the measurement of capsule deformation yielded important results that permit comparison with other polymer systems used for encapsulation. Furthermore, single-membrane and multi-membrane capsules were formed in order to improve the modulation of the capsule properties. For single-membrane capsules, resistance was mostly affected by the incubation time in poly-L-lysine (PLL), the PLL mol. wt. and concn. The increase in resistance from 0.1+-0.01 g/capsules to 2+-0.2 g/capsules was linked to a membrane thickening (35-120 mm) and a decrease in permeability (150 to 40 kDa). Thus, it was not possible to modify resistance and membrane permeability independently. Multi-membrane capsules with a resistance comparable to single-membrane capsules could be formed using various combinations of PLL mol. wts., and enabled uncoupling of permeability and resistance properties. [on SciFinder (R)]